The present invention relates to processes for controlling residual monomers while making copolymers of tertiary amino-monomer and vinyl-functional monomer able to undergo Michael addition.
Copolymers of tertiary amino-containing monomers and vinyl-functional monomers are useful in liquid detergent compositions for machine or hand dishwashing. For example, the copolymers are useful to maintain suds in hand dishwashing compositions. Such copolymers are also useful for products in the laundry field for a product having improved grease and soil removal properties, and in products in the personal care field, particularly hand soaps, body washes, shampoos, shaving creams, shaving gels and dephiliatories, which have improved foam retention. There is also a need for such polymers for improved oil field chemicals, agricultural chemicals, fire-fighting foam, detergents, mining chemicals, flocculants and coagulants.
The present inventors discovered a problem. Namely, they discovered that copolymers of tertiary amino-containing monomers and vinyl-functional monomers formed monomers when heated. The present inventors also discovered the monomers resulted from unstable Michael addition adducts of the copolymers and vinyl-functional monomers which formed during production of the copolymer. The vinyl-functional monomers can be liberated from the adduct under certain conditions to be potentially toxic.
For purposes of this specification and claims, the term copolymer encompasses polymers of two or more different monomers, e.g., bipolymers (two different monomers) or terpolymers (three different monomers).
The present invention solves the aforementioned problem in that it has been surprisingly discovered that these polymeric materials can be made with a negligible amount of undesirable adducts or monomers.
In the present invention, adduct formation is prevented/minimized by performing at least one of the following steps in a process for making copolymers from tertiary amino monomers and vinyl-functional monomers:
1. Avoid formation of adduct by separating the tertiary amino monomer (e.g. dimethylaminoethyl(meth)acrylate) from the vinyl-functional monomer prior to polymerization.
2. Avoid formation of adduct by avoiding contact of water with a mixture of the tertiary amino monomer and the vinyl-functional monomer prior to polymerization.
3. Conduct polymerization at a high temperature (typically about 70 to about 90xc2x0 C., preferably about 80 to about 90xc2x0 C.) and at a suitable pH (typically about 3 to about 10, preferably about 4 to about 8, most preferably about 4 to about 6) to cause the adduct formed to be unstable and revert to monomers. Thus, monomers bound by the adduct will be liberated to copolymerize.
Preferably, acid, e.g., mineral acid or citric acid, which is one of the reactants is fed to the reactor before the monomers.
Thus, the present invention provides methods for making compositions for hand dishwashing, personal care, particularly hand soaps, body washes, shampoos, shaving creams, shaving gels and dephiliatories, which have improved foam retention, improved oil field chemicals, agricultural chemicals, fire-fighting foam, detergents, mining chemicals, flocculants and coagulants.
The present process has many advantages. Conventional processes attempt to reduce monomers by employing high initiator concentration and long reaction times. In contrast, the present invention reduces monomer with less initiator and less reaction time than conventional processes for producing low residual monomer polymers. This saves processing time conventionally needed to react residual monomers and saves energy. Also, the present process has a synergistic benefit because the lower concentration of ingredients causes adducts to dissociate faster in the present process.
These and other objects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims.
All percentages, ratios and proportions herein are by weight, unless otherwise specified. All temperatures are in degrees Celsius (xc2x0 C.) unless otherwise specified. All documents cited are, in relevant part, incorporated herein by reference in their entirety.
Additional background on compositions and methods of use is provided by PCT International Application Nos. PCT/US98/24853, PCT/US98/24707, PCT/US98/24699 and PCT/US98/24852, all incorporated herein by reference in their entirety.